Transmission interchangability...

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Will the TH700R4 from an '88 3/4T 4x4 fin into an '85 Suburban 4x4. My "'Burban originally had a 700 and I swapped in a TH350 using an adaptor. It
was a desperation move! I aint complaining, it works AWESOME! The thing is, the friend of mine that just bought the truck doesn't want the 700 and I need one with 4.10 gears. All he will be using the truck for is to tow his skid loader and push snow. So I offered to swap him straight up trans for trans. BUT, only if they will swap straight up... Any help on this? if there will be ANYTHING more than R&R, I aint gonna do it! I know I will need a lock-up kit if I wanna use that feature(I took the few electronic items out of my 'Burban)!
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. . . . Transmission interchangability... Group: alt.autos.4x4.chevy-trucks Date: Sun, Oct 26, 2003, 6:39pm From: shades snipped-for-privacy@netins.net (Shades)
  Will the TH700R4 from an '88 3/4T 4x4 fin into an '85 Suburban 4x4.
My "'Burban originally had a 700 and I swapped in a TH350 using an adaptor.
It was a desperation move! I aint complaining, it works AWESOME! The thing is, the friend of mine that just bought the truck doesn't want the 700 and I need one with 4.10 gears.
All he will be using the truck for is to tow his skid loader and push snow. So I offered to swap him straight up trans for trans. BUT, only if they will swap straight up...
      Any help on this?
if there will be ANYTHING more than R&R, I aint gonna do it! I know I will need a lock-up kit if I wanna use that feature(I took the few electronic items out of my 'Burban)! =========== =========== Shades, as long as all you did was change out the tranny using the th350 conversion....the only things you need to worry about is the following.
Bell housing bolt pattern, conditional upon each trucks engine type.
Throttle valve cable must be reinstalled.
Lockup must be hooked up to keep the unit from overworking.
I would suggest you consider this trade out very carefully before you do it. The price difference between rebuilding a TH350 and a 700R4 is several hundred bucks, as much as 6-8 hundred dollars difference, depending on who you ask.
any whooo...... as long as you can still hook up the tv cable to your carb linkage, you wire in the lock-up, and the engine sizes for the bolt pattern are the same.......you will be okay with everything else.
marsh ~:~
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Thank you, Marsh! Yes, all I did was buy the adapter(the aluminum 'filler' between the trans and the t-case) for the 700-350 swap and used a short-shaft 350 and cut, I think it was, 1 1/8 inches off the output shaft. As far as power-plants go. I have a 350 and his has a 6.2 diesel... Will this be a problem? Thanx again Marsh...
(Shades)
Will the TH700R4 from an '88 3/4T 4x4 fin into an '85 Suburban 4x4.
My "'Burban originally had a 700 and I swapped in a TH350 using an adaptor.
It was a desperation move! I aint complaining, it works AWESOME! The thing is, the friend of mine that just bought the truck doesn't want the 700 and I need one with 4.10 gears.
All he will be using the truck for is to tow his skid loader and push snow. So I offered to swap him straight up trans for trans. BUT, only if they will swap straight up...
Any help on this?
if there will be ANYTHING more than R&R, I aint gonna do it! I know I will need a lock-up kit if I wanna use that feature(I took the few electronic items out of my 'Burban)! ====================Shades, as long as all you did was change out the tranny using the th350 conversion....the only things you need to worry about is the following.
Bell housing bolt pattern, conditional upon each trucks engine type.
Throttle valve cable must be reinstalled.
Lockup must be hooked up to keep the unit from overworking.
I would suggest you consider this trade out very carefully before you do it. The price difference between rebuilding a TH350 and a 700R4 is several hundred bucks, as much as 6-8 hundred dollars difference, depending on who you ask.
any whooo...... as long as you can still hook up the tv cable to your carb linkage, you wire in the lock-up, and the engine sizes for the bolt pattern are the same.......you will be okay with everything else.
marsh ~:~
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yes
the diesel torque converter is an entirely different animal than a converter for a gas rig
plus the wiring in the pan is vastly different
(Shades)

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Different how with the converter??? And as for the wiring, what could be different? The only electric or electronic item is the lock-up and that could be run by a toggle switch!
(Shades)

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I think he's using wiring as a euphemism for the hydraulic circuits in the valve body. a diesel's TC will have a significantly lower stall speed than a gasser and the tranny's governer and shift points need to be set for the diesel's much much lower redline.
-Bret
(Shades)

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it's pretty apparent that he's never seen all the different wiring diagrams for 700's...............over 20 total, depends on year, model, engine, etc etc etc etc
if he wants to e-mail me with an address, I'll send him a copy of a tech bulletin that details the wiring diagrams, plus a trans model (that's what those labels loke '7TKM' stuck to the top of the bell housing mean) vs vehicle print-out (40 pages or so)
the same goes for anyone else that's interested, please use the subject line 'request for 700 info' so I can use a 'message rule' to shunt them into a separate folder
G
(Shades)

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WHAT IS DIFFERENT WITH THE TORQUE CONVERTER? Please! What will the difference between the wiring mean when it comes to an aftermarket, stand alone lock-up control?
(Shades)

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stall speed and some had a 'poppet valve' arrangement to kick it out of lock-up when decelerating
various models use prresuure switches in series with the solenoid coil, to enable or delay loch-up until certain conditions
my offer of the 700 information is open to all, just send me an e-mail with a subject line of 'request for 700 info' along with a mailing address
G
(Shades)

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Gary, so basically everything will work, Right? Stall speed being low is fine! No lock-up decelerating is fine! As long as the lock-up will work with an aftermarket, stand alone lock-up control and the converter will bolt up, its all good!!! Anything else that will allow the 700 to not FIT into and BOLT up and OPERATE in my gas 'Burban?
(Shades)

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OK
I'll say it once more
you DO NOT WANT a diesel converter behind a gas engine
been there, tried it, it doesn't work worth a crap
buy a remanned converter from Precision of New Hampton, IA
model 4842G, or 4842RV if you plan to tow
(Shades)

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Gary, stop offering their services. They will not sell to individuals. Unless you want to offer your services as an intermediary transmission shop to purchase, and drop ship?
~KJ~
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What are the differences between the 350, 400, and 700 trannys? Why is the 350 more durable (according to scrib) and the 700 less?
~KJ~
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I'm sure Gary can give the details, but here's the basics..
the TH350 and TH400 (3L80) are 3 speed non overdrive vacuum modulated transmissions that came with or without lockup convertors.
the TH700-R4 (4L60/4L60E) is a 4 speed overdrive throttle valve (4L60) or electronically (4L60E) modulated transmission with a lockup convertor (did the very early ones come non-lockup,G?)
a TH700-R4 is more or less the same strength as a TH350 when the selector is in "D". it is weaker (in stock form) when in OD because the road simply has leverage over the input shaft. there were huge probs when the 700-r4 first came out because it was one of the very first 4 speed autos put into a truck and ppl simply didn't know their limitations. properly built, a 700 is plenty strong although it'll never be as strong as a built TH400.
HTH, Bret
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I've heard the OD wasn't very strong on them.
My new TH700R4 has "automagic" od. My old one had the D with a circle around it. Dunno if I like that one......
How obvious should it be/feel when it locks up, or goes into OD (is OD locking up, or is there a "fifth gear" with a ratio of 1:1)
Much confused about locking upness. A tc can lock up, and a tranny as well? Whets the point of the TC not locking up, isn't that where the 5% or so is lost on highway? Why bother to "lock" a tranny, when you could just have a 1:1 gear ratio?
</end stupid questions>
~KJ~
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<SNIP>

actually 3rd gear is 1:1, OD is .70:1 It should be fairly obvious when the TC locks up, if you've got 3.73 gears it should lock up at about 40 MPH cruising. if you have a modified exhaust, lockup can be heard when the engine stops "droning" and individual exhaust pulses can be heard. OD isn't locking up, "locking up" is when the ECU (Engine Control Unit) activates a solenoid in the pan which allows fluid pressure to press a clutch against the front cover, eliminating any slip in the convertor.

no, Lockup is the elimination of TC slip.

the point to locking the TC is to save gas. with the convertor locked, the engine will be turning 200-400rpm slower (depending on load). your final drive will be 0.70:1 in a 700-r4, also slowing the engine RPM's saving an assload of gas.... around 30% better mileage.
-Bret
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not
I'll look for it locking up, I might have some more questions about this later on...
~KJ~
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a couple of additions in-line

the 400 never came OEM with a lock-up

no
the early 200's and Th-125 (front wheel drive) were non-lock-up, but the 700 has been a lock-up from Day One

I explain it as a see-saw, with the long end occupied by the truck's mass, the short end by the engine torque, and the pivot point is the rear planet set, which is what usually goes first
actually, the rear planet is in OD mode in both 2nd and fourth

I prefer the 350 or 700 over the 400 because there is no problem with leakage in the oil circuits between the case and center support, which is the 400's down-fall
Also, the stock 400 converter is a bit 'doggy' off the line, but using an Allison 540 converter cures that problem.

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not even the very early 90's units pre-4L80E? I'm suprised by that.

My wife had an Olds Achieva (God I hated that car) that had the TCC disabled as it wouldn't unlock.... I've been told it's super common for a TH125

the gear set fails before the band slips? I'm getting the 'vette band servo put in my truck next week.
-Bret
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nope
yeah, the solenoid that controls it develops a small leak when it's supposed to be closed
the leak is enough to keep the TC control valve shifted

depends on usage
heavy useage, rear planet, especially if abused
medium usage, either 3/4 clutch pack or band slips in 4th and burns..........the reverse input drum, against which the band applies is spinning backwards in respect to engine rotation in 1st, this helps to self-apply (assists the servo in wrapping it tighter) in 2nd, but in 4th, the drum spins the same direction as the engine, which makes it more prone to slip without enough clamping force
grandma-type use, 3-4's wear out

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